Peña Blanca Lake is a reservoir in Arizona, United States, located 18 miles (29 km) northwest of Nogales.[1] The facilities are maintained by the Coronado National Forest division of the USDAForest Service. The lake was created in 1957 by the Arizona Game and Fish Department.[2] In 2008, the lake was closed to clean mercury contamination within the sediment, thought to be from old mines in the area. [3] The lake was reopened in August 2009.[4] In 2013, an Arizona Department of Environmental Quality report showed that mercury levels were similar to those before the lake was drained and dredged. One potential cause for the high mercury could be naturally occurring mercury seeping through the faults or a spring in the lake, though these claims are still under investigation. [5]